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Control valves choked flow

A4.3) reducing to the choked gas equation (9.2). But while the FUGSE will be valid at either end of the range of pressure ratios, the fact that the sine function joins the extremes in a conveniently smooth manner does not guarantee that the formula will be accurate at intermediate values. This appendix examines how closely the FUGSE matches direct data and the nozzle-based method for calculating control valve gas flow. [Pg.344]

In order to avoid the need to measure velocity head, the loop piping must be sized to have a velocity pressure less than 5% of the static pressure. Flow conditions at the required overload capacity should be checked for critical pressure drop to ensure that valves are adequately sized. For ease of control, the loop gas cooler is usually placed downstream of the discharge throttle valve. Care should be taken to check that choke flow will not occur in the cooler tubes. Another cause of concern is cooler heat capacity and/or cooling water approach temperature. A check of these items, especially with regard to expected ambient condi-... [Pg.422]

Choking, or expansion of gas from a high pressure to a lower pressure, is generally required for control of gas flow rates. Choking is achieved by the use of a choke or a control valve. The pressure drop causes a decrease in the gas temperature, thus hydrates can form at the choke or control valve. The best way to calculate the temperature drop is to use a simulation computer program. The program will perform a flash calculation, internally balancing enthalpy. It will calculate the temperature downstream of the choke, which assures that the enthalpy of the mixture of gas and liquid upstream of the choke equals the enthalpy of the new mixture of more gas and less liquid downstream of the choke. [Pg.100]

Now it appears that the value of may be estimated by using the loss coefficient K determined at choking provided K is not too small. This is unlikely since in most valves effective flow control occurs at very small throat area when the valve is in the 10-30% open range. The loss coefficient is determined from the pressure loss across the valve and the velocity in the upstream pipe at choking. [Pg.1349]

The flow coefficient Cv is determined by calibration with water, and it is not entirely satisfactory for predicting the flow rate of compressible fluids under choked flow conditions. This has to do with the fact that different valves exhibit different pressure recovery characteristics with gases and hence will choke at different pressure ratios, which does not apply to liquids. For this reason, another flow coefficient, Cg, is often used for gases. Cg is determined by calibration with air under critical flow conditions (Fisher Controls, 1977). The corresponding flow equation for gas flow is... [Pg.329]

In order to overcome the difficulties associated with the non-choked fuel-flow system and the fixed fuel-flow system, a variable fuel-flow system is introduced the fuel gas produced in a gas generator is injected into a ramburner. The fuel-flow rate is controlled by a control valve attached to the choked nozzle according to the airflow rate induced into the ramburner. An optimized mixture ratio of fuel and air, which is dependent on the flight altitude and flight velocity, is obtained by modulating the combustion rate of the gas-generating pyrolant When a variable fuel-flow-rate system is attached to the choked nozzle of the gas generator, the fuel-flow rate is altered in order to obtain an optimized combustible gas in the ramburner. This class of ducted rockets is termed variable fuel-flow ducted rockets or VFDR . [Pg.447]

Even after we have made these two unlikely assumptions, the height of hot water in the draw-off sump must still be 56 in above the center-line of the draw-off nozzle. If not, the water would begin flashing to steam, as it experienced a pressure drop of 2 psi, flowing across the control valve. The evolved steam would then choke the water flow, reducing the pressure drop across the control valve until the pressure drop equaled the depth (or head) of water in the draw-off sump. [Pg.132]

The rig consists of four 600-ml high-pressure sample cylinders. Usually, two are filled with water (brine), and two are filled with oil. With the aid of four motor-driven high-capacity piston pumps, water and oil are pumped through the choke valves. The four pumps are independent of each other, but in most of the experimental series the total flow has been kept constant. The pressure drops through the choke valves are back-pressure controlled. The pressure in the separation cell is regulated by a back-pressure controlled valve. The maximum pressure in the cell is 200 bar. The cell is filled with gas, inert or natural gas, to the desired pressure before the filling of water and oil into the separation cell starts. The separation cell (450 ml) is... [Pg.600]

Task 1 Verify the Correlation For the HP letdown control valve in Figure 16.9, the nonchoke flow correlation was used in DCS to model the letdown valve. Is it correct To answer this question, the conditions for choke flow were inspected from the manufacturing manual in which two equations were found as... [Pg.363]

For the control valve at hand, the ratio of the inlet pressure (624.7psia) and outlet pressure (164.7 psia) is only 26%. Thus, the choke flow equation (16.10) is applied to give the letdown flow of 71.2 Klb/h based on the value position at 75% openning. The choke flow rate is smaller than the nonchoke flow. By correcting this mistake, there is still a large imbalance in the HP header. What else went wrong The search continues. [Pg.363]

Feed back control A small pilot line connects the discharge side pipe of a flow control valve to the actuator/diaphragm. Ary increase in flow beyond the required flow is sensed and conveyed to the actuator which then throttles the valve plug to reduce the flow. This pilot line diameter should not be less than 10% of diameter of main downstream line or else it will not convey the downstream conditions fast enough or may get choked. [Pg.253]

Hence, we can measure the fuel flow, correct both the fuel flow and power to ISO conditions, and then eompare the results to the expected fiiel consumption from Figure 4. The deviation in this case is the degradation parameter we ean monitor over time. The problem most will face for this rule is a reliable measurement of the fuel flow rate. Many installations either have missing or inaccurate fuel meters. This can be substituted for by ealeulating the fuel flow. For machines with Mark V or VI controllers, we can use the choking condition on the gas control valve (GCV) to do this. A robust approach then would be to compare the calculated to the measured value (if available) and use it accordingly in the fuel consumption rule. [Pg.340]

Liquid flow through a control valve will be increased, when the pressure drop (dp) across the valve is increased. But this flow increase will be stopped, when choke flowthrough a control valve is reached. Further increase control valve pressure drop above this minimum choke flow control valve pressure drop (dp choke), flow through the control valve will not be increased. A liquid control valve flow capacity curve (flow versus square root of control valve pressure drop) is shown in Figure 10 [2]. [Pg.136]

The mininium choke flow control valve pressure drop (dp choke) for a liquid control valve can be estimated by following equation. [Pg.136]

The maximum flow (Q max, in gpm) throu a liquid control valve is choke flow. It is calculated by following equation ... [Pg.136]

The issue becomes how choked flow is integrated into liquid valve sizing. Fisher Controls [15,16] defines a pressure recovery coefficient as follows ... [Pg.43]


See other pages where Control valves choked flow is mentioned: [Pg.2]    [Pg.2346]    [Pg.92]    [Pg.356]    [Pg.54]    [Pg.54]    [Pg.170]    [Pg.308]    [Pg.171]    [Pg.225]    [Pg.2101]    [Pg.332]    [Pg.2556]    [Pg.2556]    [Pg.340]    [Pg.434]    [Pg.74]    [Pg.74]    [Pg.85]    [Pg.86]    [Pg.941]    [Pg.2536]    [Pg.2536]    [Pg.305]    [Pg.2350]    [Pg.357]    [Pg.97]    [Pg.1382]    [Pg.719]    [Pg.141]    [Pg.125]   
See also in sourсe #XX -- [ Pg.329 ]




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